Virtually all automated storage & retrieval systems (AS/RS) installed before 1990 can benefit from modernization.

That was certainly the case with a 20-year-old mini-load automated storage and retrieval (AS/RS) system at Pratt & Whitney's Middletown, Conn., manufacturing facility. There, the United Technologies Corp. division manufactures components, assembles and tests gas turbine engines for military, commercial and industrial applications.

While the mechanical system was still getting the job done, the control system was obsolete. Disruptions were a daily occurrence.

The solution was to overhaul the motors, controls, operating system and measuring system while maintaining the integrity of the original storage/retrieval machines (Retrotech Inc., 585-924-6333).

The result has been a system as reliable as when it was new, according to Dave Searle, tooling manager at the Pratt & Whitney facility. "Since the upgrade of the system, I almost never hear of a downtime condition from a pan jam or a failure of the crane," says Searle. "Uptime has improved dramatically."

Originally commissioned by the Atomic Energy Commission, Pratt & Whitney has operated the 1,100 acre site since 1965. The location includes 2.3 million square feet of space and 25 buildings.

Just as the plant was originally built for another purpose, the AS/RS was originally installed at another location in 1985. It was disassembled and moved to Middletown in 1994. The system is used to store and manage all of the production tooling used in the production of gas turbine engines, a variety of small machine parts and some maintenance and repair supplies.

In all, the 28-foot high unit features three storage/retrieval machines and 4,200 storage locations.

Inventory stored in the system is dispersed to 45 point-of-use tool cribs located in the two primary manufacturing buildings. Stock outs at those locations, which could be caused by disruptions to the AS/RS, can slow down the line and impact productivity. "We try to maintain minimal inventory on the floor, so any shortage caused from losing the ability to pull stock from the AS/RS, we take very seriously," says Searle.

Over the years, the frequent repairs created time-consuming maintenance issues and hindered the smooth operation of the shop floor. Physical errors were caused not so much by picking the wrong part, but by tray jams, extractor pin jams and misalignments. Meanwhile, the software was still resident on a pre-Pentium computer, which imposed severe limitations on the system's capabilities.

"The computer operating the system was installed in 1986," explains Bob Hand, a Pratt & Whitney project manager who worked on the upgrade. "Even though we maintained the inventory on our enterprise system, the operating system was old and the controls were obsolete."

To compensate, the company was storing safety stock in a shelving location just in case the system went down. "Near the end, one of the six aisles was failing so often, we had to move the inventory out of there," says Hand.

Pratt & Whitney considered replacing the AS/RS with traditional storage to eliminate the cost of maintaining the unit. "When we realized how much square footage we would need for racks and bins, we realized it would be more expensive to be without it," says Hand.

Four goals drove the upgrade.

One was to improve uptime and reliability.

A second was to ensure that any upgrades used over-the-counter hardware, and that the source code for software would be readily available. As well, replacement on-board components would have to be specified and fitted in a way that would simplify all future maintenance and troubleshooting needs.

The third was a wish to retain components that were still serviceable, including enclosures, certain sensors and some mechanical components.

The fourth was timeliness, Hand recalls. "We had to get the first aisle done quickly so as to remain fully operational."

The upgrades included new programmable logic controllers (PLCs) for the storage/retrieval machines and a DeviceNet communications network that provides the link between sensors, actuators and the PLCs.

New software was added to interface with Pratt & Whitney's enterprise system, which maintains the inventory system.

The original positioning system was upgraded to an optical laser distance-measuring system that is accurate to within 10 mm for precise positioning of the storage/retrieval machines. Laser guidance also now directs the lateral extractor that retrieves pans from their storage location.

The extra accuracy that comes from the laser system has meant an end to jams from misalignments.

One benefit of a new control system is better information about the operation of the system. That resulted in reduced maintenance costs. "From a reporting stand point, the old system was adequate for our needs," says Searle. "But from a maintenance standpoint, we're able to monitor the unit in real time. The system records any failures and calculates any down time. That gives us a perspective on repeat failures we didn't have before and allows us to address maintenance issues before they become a problem."

At the end of the day, the combination of reduced maintenance and increased uptime has breathed new life into the old system. "The upgrade has added many years of life to the AS/RS, and reliability is absolutely improved," says Hand.